1. Field of the Invention
The present invention relates to audio video products. More particularly, the present invention relates to audio video devices configured for connection to host computers.
2. Description of the Related Art
With the advancements in imaging technology and increased computer processing power, much attention has been focused on the acquisition and processing of audio/video data in personal computers. Currently, video sources provide audio and video data in either or both of analog and digital formats. In order to facilitate the processing of video signals by computers, video boards having image acquisition capabilities are used.
These boards typically accept a video signal in either an analog or digital format and transmit the signal in a digitally encoded format to the computer. Analog signals, in particular, require conversion to a digital format and in many cases compression before the data is transmitted to the host computer. Analog video signals are typically organized into frames, typically 30 frames or 60 fields per second. An analog to digital converter (ADC) digitizes the incoming video signal in response to synchronization information embedded in the analog video signal.
The resulting digitized frame samples are temporarily stored in a frame acquisition buffer and then transferred to the computer system memory for further processing. In contrast, a digital video source (e.g. a digital camcorder) provides a digital video signal to the video board via the digital video port. Since the digital video signal already comprises a stream of digitized video frames, the ADC on the video card is bypassed and the digitized frame data is forwarded directly to the frame acquisition buffer in the card. The data is then transferred to the computer via a communications cable. Further, it may be compressed in a standard format, such as MPEG, before transmission to the host computer. The audio signal is also converted where necessary to digital formats and stored in a synchronized manner with the stored digital video data frames.
Audio boards are also used with computers to provide enhanced audio signals. In some cases external audio cards are coupled to a computer to add audio processing capabilities to those available from the host computer.
While both video capture cards and audio cards are available in an external form and having USB compatibility for communication via a USB cable to the host computer, providing separate external devices requires multiple communications cables for connection to the host computer, as well as multiple enclosures and power cables. Moreover, communication between the video module and the audio module in such a configuration requires signals to be routed via the host computer.
It is therefore desirable to provide an improved device for providing audio and video signal processing.